Network Calculus. Part 1. Theoretical foundations

When trying to apply the classical queuing theory to the study of the characteristics of modern multiservice packet networks, certain difficulties arise due to the peculiarity of traffic and service disciplines in such networks. In these conditions, a possible way out is to use the perspective direction of modeling and analysis of infocommunication networks and systems - Network Calculus theory. The first part of the article shows the difference between the Network Calculus theory and queuing theory. Five main properties of the theory of Network Calculus are given, which allow analyzing any infocommunication network or system. The history of origin and the current state of the theory are presented. The mathematical basis of the Network Calculus is briefly described. The main points of the two directions of the theory, deterministic and stochastic, are considered. In each direction, the basic concepts are defined - the arrival curve and the service curve, as well as the main characteristics - packet delay and backlog. Open questions and unsolved problems are indicated. In the second part of the article, various examples of practical application of Network Calculus theory to the analysis of infocommunication networks and systems will be considered.